Non-penetrating filtration surgery

ABSTRACT

Apparatus for ophthalmic surgery, especially non-penetrating filtration surgery, comprising a laser source that ablates sclera tissue at steps of intermediate thickness. Optionally, the beam is scanned using a scanner and its results viewed using an ophthalmic microscope.

RELATED APPLICATIONS

This application is a continuation in part of PCT PCT/IL00/00263, filedMay 8, 2000 in the Israel receiving office and which designates the US,the disclosure of which is incorporated herein by reference. Thisapplication also claims the benefit under 119(e) of 60/331,402, filedNov. 15, 2001.

FIELD OF THE INVENTION

The present invention is related to the field of Glaucoma treatmentusing laser ablation.

BACKGROUND OF THE INVENTION

Glaucoma is an optical neuropathy associated with increased intraocularpressure. The mechanism of the disease is not fully understood. However,the most effective therapy appears to be reducing the intraocularpressure, for example using medication or implants. Further damage tothe optic nerve is thus prevented or reduced.

One procedure that has been suggested is non-penetrating trabeculectomy,in which a portion of the sclera overlying the Schlemm's canal isremoved, allowing aqueous humor to leave the eye. It is desirable toremove only part of the thickness of the sclera, preventing penetrationinto the eye. However, this procedure is difficult to perform with aknife. Typically, the effect of the procedure can only be gauged after awhile, since intra-ocular pressure is only measured after the procedureis completed. As the pressure of the knife causes trauma to the eye, thepressure is not usually measured until the eye has somewhat recovered,such as the next day. In laser based procedures, such as SLT and ALT,pressure is sometimes measured after the procedure is completed, toensure that the intra-ocular pressure did not suddenly rise.

U.S. Pat. No. 5,370,641 to O'Donnell, the disclosure of which isincorporated herein by reference, describes using an Excimer laser or anErbium laser to ablate the sclera overlying the Schlemm's canal and thetrabecular meshwork thereby forming a porous membrane. The laser spotsize and treatment area are not described. This patent states that whena sufficient amount of the corneoscleral bed is removed, aqueous humorcomes through the remaining ultra-thin Schlemm's canal and trabecularmeshwork and the energy of the laser is absorbed by the out-flowinghumor, creating a self-regulating end point.

However, even though many years have passed since this patent wasissued, the method taught in the patent has not found wide-spread use,in spite of a great need in the art of treating Glaucoma, a disease forwhich there is no completely satisfactory treatment. One possible reasonis that the '641 patent uses lasers that remove very thin (micron sized)layers of material. Further, once even a weak percolation starts, thelaser is only effective to remove the percolation, not further tissue,while at the same time possibly causing thermal damage to the underlyingtissue. This thermal damage may be a cause of later scarring.

SUMMARY OF THE INVENTION

An aspect of some embodiments of the invention relates to apparatus foreffecting and controlling a non-penetrating filtration procedure, usingan ablation source that remove a layer of tissue of intermediatethickness, for example, between 5 and 30 microns. In an exemplaryembodiment of the invention, the ablation source and parameters areselected so that the removal depth is smaller than a desired finalmembrane thickness but greater than a thickness of percolation which maybe expected prior to the desired membrane thickness being achieved. Inan exemplary embodiment of the invention, the ablation source isabsorbed by the percolation. Optionally, the ablation parameters areselected so that the process of ablation is self-curtailed when thepercolation is fast enough to create a layer the thickness of theablation depth. In an exemplary embodiment of the invention, theablation source is selected to have the flexibility to provide more thanone meaningful ablation depth.

In an exemplary embodiment of the invention, the laser is a diode laseroperating at 1.8 microns, a ¹³C¹⁶O₂ isotope laser or an Erbium:YSGGlaser. In contrast to Erbium:YAG lasers, for example, the above listedlasers have an ablation depth that is greater than the small ablationdepth of 1-3 microns of the Erbium:YAG laser. This is also thepercolation thickness which may be expected to exist, in many cases,long before the membrane is thin enough. While the thickness of thepercolation is dependent on the time between pulses, practical reasons,such as laser pulse rate, thermal damage and shock wave damagepotentially caused by the laser pulse transfer generally prevent thepractical use of low (e.g., micron) ablation depth lasers such as theExcimer and Er:YAG for the application of ablation. It should be notedthat in the field of skin resurfacing, the standard (non isotopic)¹²C¹⁶O₂ laser rules supreme. While this laser does have some degree offlexibility the minimum ablation depth (where a minimum of charring isproduced) is about 30 to 50 microns, which may not be fine enough forsome patients and/or protocols. In addition, it should be noted thatunlike in skin applications, thermal damage to the membrane and/or othereye tissue does not heal as readily and is more likely to scar, forexample due to the lack of underlying healing tissue.

In an exemplary embodiment of the invention, the apparatus includes ascanner for automatically scanning an area of the eye using a laserspot, thereby ablating over the entire area. Optionally, a continuousscan is used, with the laser beam on at all times. A potential advantageof using a scanner is the ability to provide a large total amount ofenergy to a large area of the eye using a relatively inexpensive laserand scanning the beam over the area. Optionally, a pulsed ¹³C¹⁶O₂ lasersuch as an ultrapulse laser with a scanner, for example, a galvanometricscanner, is used.

Another potential advantage of using a scanner is that a uniformpercolation profile (or another desired profile) may be achieved.Optionally, a uniform final tissue thickness is created by the ablation.Alternatively, different tissue types or areas may have differentthickness, so that a uniform percolation is achieved. In some cases, theablated sclera or cornea thickness will vary responsive to theunderlying tissue. In some embodiments of the invention, the desiredpercolation rate is a factor that controls the process and/or ablationparameters.

In some embodiments of the invention, a reservoir is ablated in thesclera and/or cornea for collecting the percolating aqueous humor.

In one embodiment of the invention, the laser beam is optically combinedwith a visual system, using an optical combiner, to allow monitoring ofthe procedure. Optionally, the visual system is a ophthalmic microscope,for viewing the area of ablation by a physician performing theprocedure. Alternatively or additionally, the visual system is anautomatic vision system. Optionally, the optical combiner comprises amicro-manipulator, allowing the physician to change the laser aimingpoint and/or scan area. It is noted that standard micro-manipulators andbeam combiners do not support an input from a spatially scanning laserbeams.

An advantage of monitoring using a human or automatic visual system isthat the ablation at a particular location on the eye can be stopped assoon as the aqueous humor starts percolating out, without requiring anoptional self-limiting behavior of the a laser beam to take effect.

An aspect of some embodiments of the invention relates to using asensor, for example, an automatic vision system for monitoring anon-penetrating filtration procedure. In one embodiment of theinvention, the vision system detects percolation of liquid from theablated sclera or cornea, thus identifying that ablation at thepercolating point should be stopped. Optionally, this allows a greaterdegree of safety. Alternatively or additionally, the vision systemcontrols the scanner (or laser) to reduce or eliminate the scanning ofthe laser at some points, while continuing the scanning at other pointsin the eye.

In an alternative embodiment of the invention, a pressure sensor is usedto measure an intra-ocular pressure, during and/or after a procedure.The measurement may be, for example, continuous or intermittent. Themeasurement may be performed during pauses in the procedure and/or maybe performed while the procedure continues. In some cases, for example,if the pressure goes down this may indicate a successful percolation. Ifthe pressure does not go down enough, this may indicate that a largerarea should be ablated. If the pressure goes down too much, possibly theprocedure should be stopped at once. This sensor may be coupled to thesystem to operate automatically. For example, an input from the sensormay be used to automatically stop or change ablation parameters.Alternatively, the sensor is used to generate an alarm, through theablation system or on its own (e.g., by setting a pressure at which tosound an alarm). Alternatively or additionally, the sensor is usedmanually, for example, with a physician entering new ablation parametersinto the ablation system (e.g., using a suitable input) based on thepressure reading and/or entering pressure values which are interpretedby the ablation system to change its parameters.

Alternatively or additionally to using a pressure sensor, an ablationthickness sensor or a sclera thickness sensor is used to determine ifablation is to continue and/or under what parameters.

In an exemplary embodiment of the invention, the pressure sensor is anon-penetrating sensor that optionally contacts the outside of the eye.Alternatively, a penetrating pressure sensor is used, for example, aspart of a system that penetrates the eye and controls the intra-ocularpressure by providing or removing fluid, as needed.

An aspect of some embodiments of the invention relates to an eyeprotector. In an exemplary embodiment, the eye protector preventsablation by the laser outside of a predefined area, for example byphysically blocking the laser light. Optionally, the eye protector isadhesive to the eye. Alternatively or additionally, the eye protectormaintains open, during the procedure, one or more flaps formed in theeye. Alternatively or additionally, the eye protector is disposable.

There is thus provided in accordance with an exemplary embodiment of theinvention, apparatus for ophthalmic surgery on an eye comprising:

-   -   a laser source that generates a laser beam, adapted to ablate a        scleral tissue thickness of between 5 and 30 microns in a single        shot; and    -   an ophthalmicly effective position controller. Optionally, the        apparatus comprises an ophthalmic microscope operative to view        an eye during an ophthalmic procedure that uses said laser beam.        Optionally, the apparatus comprises a monitor for displaying a        view of said tissue removal viewed by said microscope.        Alternatively or additionally, the apparatus comprises a beam        combiner for combining a line of sight of said laser and said        microscope.

In an exemplary embodiment of the invention, said position controllercomprises an ophthalmic frame operative to fixing a relative positionand angle of said laser source and an eye of a patient. Alternatively oradditionally, said position controller comprises a scanner comprising aninput for said laser beam and an output of a spatially scanned laserbeam. Optionally, the apparatus comprises controlling circuitry thatdrives said scanner to remove tissue in a desired pattern on the eye.Optionally, the apparatus comprises a sensor which monitors anindication of progression of said surgery, on said eye, to produce aprogression signal. Optionally, the apparatus comprises:

-   -   a camera which acquires an image of said tissue removal; and    -   an image processor that processes said image. Alternatively or        additionally, the apparatus comprises circuitry that uses said        progression signal to generate an indication of the tissue        removal state. Optionally, said circuitry uses said indication        to close a control loop of said tissue removal. Alternatively or        additionally, said indication of tissue removal state comprises        an indication of the thickness of remaining tissue in the area        of tissue removal. Alternatively or additionally, said        indication of tissue removal state comprises an indication of a        percolation rate through the remaining tissue in the area of        tissue removal.

In an exemplary embodiment of the invention, said sensor measures anintra-ocular pressure. Alternatively or additionally, said sensor is anon-penetrating sensor. Alternatively or additionally, said sensor is acontact sensor.

In an exemplary embodiment of the invention, said controlling circuitryreceives signals from said sensor.

In an exemplary embodiment of the invention, the apparatus comprises auser input, wherein said controlling circuitry is adapted to receive andinterpret entries on said input as indicating signals from said sensor.

In an exemplary embodiment of the invention, the apparatus comprises aframe attached to said combiner, which frame blocks said laser beam fromat least one part of said eye.

In an exemplary embodiment of the invention, said laser source comprisesa CO₂ laser source.

In an exemplary embodiment of the invention, said laser source comprisesan isotopic ¹³C¹⁶O₂ laser source.

In an exemplary embodiment of the invention, said laser source comprisesan Erbium:YSGG laser source.

In an exemplary embodiment of the invention, said laser source comprisesa diode laser source operated at a wavelength near 1.8 microns.

In an exemplary embodiment of the invention, said laser source comprisesa UV laser source.

In an exemplary embodiment of the invention, said laser source generatesa second, visible wavelength, aiming beam aligned with said laser beam.

In an exemplary embodiment of the invention, said laser beam is a pulsedlaser, each pulse being a single shot. Alternatively, said laser beam isa pulsed laser, a plurality of pulses being grouped as a single shot.Alternatively, said laser beam is a continuous laser that isartificially gated to generate shots.

There is also provided in accordance with an exemplary embodiment of theinvention, a method of performing a non-penetrating filtrationprocedure, comprising:

-   -   opening a flap in an eye, overlying a Schlemm's canal of said        eye;    -   forming a percolation zone adjacent said Schlemm's canal by        ablation using a laser that ablates a tissue thickness of        between 5 and 30 microns, each shot;    -   forming a reservoir in a sclera of said eye and in fluid        connection with said percolation zone; and    -   closing said flap. Optionally, forming a percolation zone        comprises cleaning away charred tissue from said percolation        zone. Alternatively or additionally, the method comprises        forming by automatic scanning with a laser. Optionally,        automatic scanning with a laser comprises automatically        controlling at least one parameter of the scanning responsive to        an effect of the laser on the tissue.

In an exemplary embodiment of the invention, said laser is a CO₂ laser.Alternatively, said laser is a ¹³C¹⁶O₂ laser. Alternatively, said laseris an Er:YSGG laser. Alternatively, said laser is a diode laser operatednear 1.8 microns wavelength.

In an exemplary embodiment of the invention, the method comprisesplacing a protective sticker on said eye prior to forming saidpercolation zone, said protective sticker having a spatial window thatadmits a wavelength of said laser and a body that block said wavelengthfrom parts of the eye other than an area to be ablated.

There is also provided in accordance with an exemplary embodiment of theinvention, a method of performing a non-penetrating filtrationprocedure, comprising:

-   -   forming a percolation zone adjacent a Schlemm's canal of an eye    -   measuring an intra-ocular pressure of said eye in response to        said forming a percolation zone; and    -   modifying parameters of said forming in response to said        measuring.

BRIEF DESCRIPTION OF THE FIGURES

Exemplary, non-limiting embodiments of the invention will be describedbelow, with reference to the following figures, in which the sameelements are marked with the same reference numbers in differentfigures:

FIG. 1 is a schematic illustration of an exemplary ophthalmologicablation system, during a non-penetrating filtration procedure inaccordance with an exemplary embodiment of the invention;

FIGS. 2A-2C illustrate the absorption of laser energy by sclera tissue,for three different types of laser source;

FIG. 2D is a graph showing the relative utility of lasers for sclerasurgery, in accordance with an exemplary embodiment of the invention;

FIG. 3A is a schematic illustration of an exemplary scanner suitable forthe system of FIG. 1;

FIG. 3B is a schematic illustration of an exemplary micro manipulatorfor the system of FIG. 1, in accordance with an exemplary embodiment ofthe invention;

FIG. 4 is a flowchart of a method of non-penetrating filtration, inaccordance with an exemplary embodiment of the invention;

FIG. 5 is a perspective view of an eye showing an exposed ablation area,in accordance with an exemplary embodiment of the invention;

FIGS. 6A and 6B illustrate a completed percolation and reservoir system,from a side and a top view, in accordance with an exemplary embodimentof the invention;

FIG. 7 illustrates an exemplary protective framework, in accordance withan embodiment of the invention; and

FIGS. 8A and 8B illustrate two alternative exemplary eye protectors inaccordance with some embodiments of the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

FIG. 1 is a schematic illustration of an exemplary ophthalmologicablation system 50, during a non-penetrating filtration procedure inaccordance with an exemplary embodiment of the invention.

Referring first to an eye 40, an exemplary filtration procedure usingsystem 50 comprises ablating parts of an area 31 of a sclera 41 and/or acornea 42 in an area 30. Some of the ablation is directed to those areasoverlying a Schlemm's canal 34 and/or trabecular meshwork 32. The sizeof area 30 is exaggerated in FIG. 1, as in many procedures, area 30 issignificantly smaller than area 31 and may comprise substantially onlythe boundary area between cornea 42 and sclera 41 that overlies theSchlemm's canal. In some procedures, however, a larger portion of thecornea may be ablated. Optionally, a scanner is used to scan a laserspot over an area of the sclera larger than the spot. A more detaileddescription of an exemplary filtration procedure and an exemplaryscanner is provided below. Also shown are optional sensors 35, 37 and/or39, described below.

The thickness of sclera tissue at area 30 prior to ablation is, forexample, 1 mm. The desired thickness of the sclera after ablation is,for example, between 10 microns and 50 microns. It should be noted thatit is desired that a complete membrane of sclera tissue be maintained,to reduce complications caused by entering the eye itself.

Laser ablation operates by light being absorbed by tissues in a thinlayer, for example between 1 and 50 microns thick and the light causingheating of the tissue, so that the absorbing tissue explodes. Thisexplosion can also cause (generally unwanted) damage by means of ashockwave produced by the explosion or by heat that is absorbed byunderlying and/or adjacent tissue. When the membrane is thin enough,fluid percolates through the membrane and covers it. This fluid isgenerally very similar to the sclera tissue, especially with regard tooptical absorption and heat dissipation properties. Thus, the fluidablates in much the same way and parameters as sclera tissue. As can beexpected, each type of laser wavelength has different interactionparameters with the sclera tissue and has further functional limitationscaused by the physical limitations of the laser, for examplecommercially viable power level and pulse rate.

It has now been determined that different types of lasers have differentutilities when used for ablation of the sclera and for non-penetrationfiltration. In particular, two properties of the laser may be ofinterest. First, the depth of ablation, which determines how large athickness is ablated at one time and, second, the matching between thefluid ablation and the sclera ablation.

In some cases, an interesting result of these two properties,self-limiting of ablation, can be achieved. For example, if a laser hasa given ablation depth and the fluid has the same ablation properties asthe sclera and the local pulse rate of the laser is low enough to allowfluid to percolate to the ablation thickness, repeated laser pulses willonly remove (the self renewing) fluid and not further ablate the sclera.In some cases, however, this self-limiting behavior can be selfdefeating or meaningless. FIGS. 2A-2C show the effects of various typesof laser on sclera tissue.

FIG. 2A shows the situation where a highly absorbed laser, such asErbium:YAG is used. Reference 43 indicates the amount of fluid thatpercolated through a membrane 48 since the laser pulse. Reference 44indicates the area that can be ablated by a single Erbium:YAG laserpulse. As can be seen, the ablation of membrane 48 cannot continue iffluid 43 percolates faster than the pulse rate. The effective pulse rateis moreover limited by the damage caused by shockwave of the laser andby the laser itself which has a limited pulse rate. If scanning isdesired, this further limits the effective pulse rate of the laser, inas much as percolation from adjoining areas may also cover the ablatedarea.

FIG. 2B shows the situation where a low absorption laser is used, forexample, a ¹²C¹⁶O₂ laser. This laser is characterized by a largeablation depth 44 (e.g., 30-50 microns as opposed to 1-3 microns of anErbium:YAG laser) and also a large thermal damage depth 46. Thus, in theconfiguration shown, the small amount of percolation does not prevent alarge thickness of sclera from being ablated. However, the remainingsclera is likely to be thermally damaged. Also, it is difficult to finetune the exact thickness of membrane 48, in as much as the depth ofablation is so large. Thus, the percolation rate, which is dependent onthe thickness of membrane 48, is more difficult to exactly achieve. Infact, the self-limiting point may be skipped by the laser inadvertentlyablating clear through the sclera. In many cases, however, even suchrough approximation may be good enough, for example, by ablatingdifferent thickness of membrane over different parts of the eye, so thatthe total effective (e.g., averaged) percolation rate is as desired,while taking care to not over-ablate the sclera and penetrate the eye.Alternatively or additionally, the local pulse rate may be selected tobe low enough (e.g., by modifying the pulse rate and/or scanningpattern) so that a sufficiently thick layer of fluid 43 percolates andserves to control the amount of actual sclera tissue ablated.

FIG. 2C shows the situation where an intermediate absorption laser isused, for example, an isotopic ¹³C¹⁶O₂ laser, an Erbium:YSGG or a diodelaser at 1.8 microns wavelength. The thickness of ablation and ofthermal damage is relatively small, especially relative to a finaldesired membrane thickness, but still greater than percolation thatoccurs when the membrane is not at its target thickness. It should benoted that there may be a variation in percolation rate between patientsand/or intra-ocular eye pressures, so that even if a same membranethickness and/or percolation properties are desired, different fluidpercolation rates may be observed during the procedure.

FIG. 2D is a graph showing the relative utility of lasers for sclerasurgery, in accordance with an exemplary embodiment of the invention thedifferent lasers are compared using a unit N which indicates thicknessof membrane 48 in units of minimum ablation thickness of the laser. Thethickness of membrane 48 is taken to be 100 microns, thus, N=(100microns/ablation thickness). If a different thickness is selected,different values of N will be generated. A more exact presentation of Nand the ablation depth (based on a minimum or typical penetration depththat provided effective ablation) is shown in a table below. The onesided “error” bars indicate the depth of thermal damage to be expected.Two bands are marked on the figure. The shaded band indicates a range ofvalues for N which apparently afford control while allowing a desiredablation to be performed. The dotted lines enclose a wider band wherecontrol is marginal but may be suitable for various applications. Ingeneral, as N is larger, finer control can be achieved, but proceduretime is longer and is in danger of being limited by non-finalpercolation. As N is smaller, less control but surer ablation can beachieved. For some lasers, it is possible to control the penetrationdepth by modifying the pulse duration and/or the energy of the pulse.However, many lasers are limited by the physical properties of the laserand/or the degree of control is not sufficient to allow a laser that isnot useful to become useful.

As can be appreciated, these indications are not absolute. For example,if the desired membrane thickness is greater, lasers with a currentlylow N may become more useful. Lasers with a high N, however, suffer frombeing self limiting when there is percolation, thus, to be effective,the laser must be able to provide multiple pulses in the time it takesfor percolation the thickness of the ablation depth to occur, if thispercolation is not the desired final effect. Also, some method ofpreventing damage from shockwave and other artifacts may be required.Thus, other useful values of N (for a 100 micron thickness) are below50, 20, 10 and 6 and/or above 2, 3, 4, 5, 7 and 10. In general, a usefulvalue of N for any thickness may depend on the precision desired insetting the thickness, so the above listed possibly useful values of Nmay apply to an N calculated using a different membrane thickness.

As can be seen, Erbium:YAG and Excimer lasers have too small an ablationthickness, while ¹²C¹⁶O₂ is marginal and Ho:YAG has too large anablation thickness. Diode lasers operated at 1.8 micron wavelength,Erbium:YSGG and isotopic ¹³C¹⁶O₂ operated at 11.2 microns wavelengthhave an intermediate ablation thickness which allows for freedom inmanipulating the thickness (e.g., by increasing the energy) and moreexact approximation of the final membrane thickness, even underconditions of partial percolation. Other lasers may be used as well, ifthey have spectral characteristics (and/or absorbency characteristics)that match the areas and lines shown in FIG. 2D. Penetration depth inwater (1/e) = approximate ablation N (for thickness of Laser Type depth100 microns) Excimer 1 micron 100 Diode at 1.8 micron 20 microns 5Holmium:YAG 100-200 microns   1-0.5 Er:YSGG 15 micron 7 Er:YAG 1-3micron 100-30  ¹²C¹⁶O₂ 30-50 micron 2-3 ¹³C¹⁶O₂ 15 micron 7

Alternatively, a laser may be selected that has a low absorption in thepercolating fluid, and an intermediate or high absorption in the scleratissue. However, this laser may not have the desired self-limitingeffect. Alternatively, a combination of laser wavelengths may be used.

The laser source is shown in FIG. 1 as a laser source 52.

The type of interaction of the laser (or other light) with the eye istypically that of ablation, especially low-char ablation. However, othertissue removing interactions may be used as well, for example,vaporization and coagulation (and then optionally removal of the damagedtissue).

Optionally, source 52 also generates an aiming laser beam (not shown),having a low power and/or being visible. The aiming beam is optionallycoaxial with ablation beam 54. This aiming beam may be formed by aseparate laser boresighted with beam 54.

In one embodiment of the invention, laser beam 54 has a spot sizesmaller than the size of area 30 that is actually ablated. Beam 54 isoptionally scanned over area 30 using a scanner 56, for example amechanical, electro-optical or acusto-optical scanner. An exemplaryscanner is described in greater detail below.

In some embodiments of the invention, the procedure is monitored throughan ophthalmic microscope 58 or other suitable optical instrument. In oneembodiment of the invention, a human viewer 62 views area 30 though aneyepiece 60 of microscope 58. Alternatively or additionally, theprocedure is imaged using an imager 64, such as a CCD camera.

In an exemplary embodiment of the invention, beam 54 (and/or optionalthe optional aiming beam) is optically combined with the line of sightof microscope 58 and/or that of imager 64, using a beam combiner 70.Optionally, combiner 70 comprises a micro-manipulator, allowing therelative location of beams 54 and the line of sight of microscope 58 tobe modified. Various types of micro-manipulators may be used, with aparticular one being described below. In an exemplary embodiment, a joystick 72 is provided on beam combiner 70 to control the relative linesof sight.

Unlike standard beam-combiners for ophthalmic use, combiner 70 isexpected to receive a scanning beam, rather than a point source. Thus,the optics of combiner 70 are optionally designed to correctly aim thebeam over a significant range of beam positions, such as ±2, ±4 or ±5 mmoff center of the micro-manipulator input axis.

The image (or image sequence) acquired by imager 64 may be used invarious ways. In one embodiment of the invention, the acquired image maybe displayed, for example using a display 66. Alternatively oradditionally, the acquired image is recorded. Alternatively oradditionally, the acquired image is analyzed using an image processor68. In some embodiments, the image and/or control parameters aretransmitted to a remote location, such as using an Internet or othercommunication network.

In some embodiments of the invention, the image analysis is used todetect the percolation of aqueous humor. Alternatively or additionally,the image processing confirms that ablation beam 54 (or the aiming beam)are within a designated safety area. Alternatively or additionally, theimage processing detects the depth of ablation, for example usingstereoscopic images, by shadow analysis and/or by virtue of thin tissuebeing more transparent. The thickness of the tissue may be thendetermined, for example, by shining a strong light into the eye andmeasuring the relative or absolute amount of light exiting through theablated tissue. Optionally, dye is provided into the eye, for exampleusing iontophoresis (or injection) and the degree of percolation isdetermined by viewing the color intensity of the percolating aqueoushumor.

The detected percolation may be used to provide feedback to the treatingphysician, for example using display 66 or via an audio alarm (notshown). Alternatively or additionally, laser 52 may be shut off or beam54 blocked, for example at scanner 56 or combiner 70. Alternatively oradditionally, the image processing results may be used to complete acontrol loop, such as by controlling the scanning parameters of scanner56.

In some cases, the laser beam may inadvertently penetrate into theeyeball. Optionally, such penetration is detected based on a flow rateof aqueous humor from the eye (which is a typically higher rate thanthat provided by percolation). Optionally, the procedure may becompleted as a penetrating filtration procedure. Alternatively oradditionally, a penetration is planned at at least one part of the eye.Optionally, the scanner is controlled to congeal and/or scar the tissueat or near the penetration area.

In one embodiment of the invention, a controller 74 is provided toreceive the image processing results and apply suitable control to lasersource 52, scanner 56, combiner 70. Alternatively or additionally,controller 74 is used for processing and displaying of data and/or forreceiving input from the treating physician, such as procedureparameters. An suitable input device 76 may be provided.

FIG. 3A is a schematic illustration of an exemplary scanner 56 suitablefor system 50. A beam 54 from laser source 52 is scanned in a first axisby a mirror 100, powered by a motor 102. A second mirror 104, powered bya second motor 106 scans the beam in another, optionally orthogonalaxis. The two mirrors may be controlled by a scanning controller 108.The scanning is optionally continuous over a defined scanned area. Insome embodiments, a same scanner may be used for scanning differentsized and shaped areas. A beam attenuator 110 is optionally provided toselectively attenuate beam 54, for particular scanned locations in area30 and 31 (FIG. 1). Attenuator 110 may be a one cell attenuator or itmay be a spatial modulator. It should be noted that many differentscanner designs can be used to generate a scanned beam, for examplescanners using rotating prisms and acusto-optical scanners.

Additional potential advantages of a scanner which may be realized insome embodiments of the invention, include:

-   -   (a) limiting the laser and/or heat damage from nearby areas;    -   (b) providing depth control of the ablation in different parts        of the eye;    -   (c) providing percolation rate control in different parts of the        eye;    -   (d) when uniform ablation is desired, allowing selection of        uniform depth or uniform tissue thickness;    -   (e) varying the scanning speed, intensity, pulse rate and/or        other parameters based on the tissue type. Controller 74 may be        used to simultaneously control laser 52 and scanner 56 to        achieve various desired laser effects; and/or    -   (f) controlling the local pulse rate to match the actual pulse        rate of the laser with the local percolation rate and a desired        percolation rate at which the procedure should be self-limiting.

FIG. 3B is a schematic illustration of an exemplarycombiner/micro-manipulator 70 for system 50, in accordance with oneembodiment of the invention. As noted above, in some embodiments of theinvention the input beam is scanned, rather than being restricted to asingle spatial location. Thus, combiner 70 is optionally designed toproperly combine the beam with the line of sight of microscope 58 overan expected range of off-axis positions of the scanning beam.

As shown in FIG. 3B, a beam 54 enters combiner 70 and is opticallyprocessed by an optical system 120, which system controls the focusingof beam 54, so that it will be focused at areas 30 and 31, as required.In one embodiment of the invention, optical system 120 is configuredand/or controlled so that beam 54 has the same focal plane as microscope58. As will be described below, this can be achieved manually orautomatically.

The optical path of microscope 58 may be delimited by an enclosing ring124.

Beam 54 is combined with the optical path of microscope 58, using a beamcombining element 122, for example a mirror that is transparent orsemi-transparent to visible light and reflective for infra-red (or thewavelength of the laser). In an exemplary embodiment of the invention, ajoy-stick 72 or other input means is provided for rotating beam combiner122, so that the relative placement of laser beam 54 and the viewingfield of microscope 58 can be controlled. Alternatively, the scanningarea is defined and/or moved using scanner 56, which may require alarger and/or wider angle beam combiner to be provided. Alternatively oradditionally, scanner 56 is provided as a single unit integral withcombiner 70.

FIG. 4 is a flowchart 200 of a method of non-penetrating filtration, inaccordance with an exemplary embodiment of the invention. First, at 202,a flap 26 (FIG. 1) is formed in the conjunctiva of the eye. At 204, aflap is formed in the sclera 41 and cornea 42. Such flaps may be formedusing any method known in the art, including using a scalpel, a laserand/or a dedicated cutting tool.

FIG. 5 is a perspective view of eye 40 showing an exposed ablation area30 and 31, in accordance with an exemplary embodiment of the invention.In one embodiment of the invention, the flaps are opened so that theyunroll in different directions. Thus, when the flaps are closed, the tipof one flap is under the base of the other flaps. This may provide astronger seal. In the embodiment shown, the two flaps open in oppositedirections, however, other angular relationships may be provided, forexample an orthogonal relationship. Alternatively or additionally, thetip of sclera flap 27 is over sclera 41, for example, so that anyswelling or inflammation will be less likely to affect the lens.Alternatively, the tip of flap 27 is over cornea 42 or, alternatively,over the boundary between the sclera and cornea.

At 205, the tools to be used are calibrated for the ablation area. Insome embodiments, the tools are calibrated before the start of theprocedure and/or periodically recalibrated during the procedure.Exemplary calibrations include: beam intensity, scanner/combineralignment and/or laser focal plane. A laser focal plane calibration maybe performed in conjunction with setting the microscope focal plane.Alternatively or additionally, a flexible focal distance combiner isused, which includes lens and/or other optical elements for varying thefocal distance.

The target area may be shown, for example as a marking on mirror 122(FIG. 3B). Alternatively or additionally, a computer display may beprovided showing an image of the eye and an estimated or imaged positionof the laser beam. In some embodiments, a computer generated displayshowing, for example, scanning parameters, is combined with microscope58, so viewer 62 can view the display via the microscope.

Depending on the particular implementation, microscope 58 and/orcombiner 70 (which may be an integral unit with microscope 58), may ormay not be in contact with eye 40 and/or ablated areas 30 and 31.

As will be described below, in an exemplary embodiment of the invention,both a percolation zone 220 (FIG. 6 below) for allowing percolation ofthe aqueous humor and a reservoir zone 222 (FIG. 6 below) for storingthe up-welling humor until it is absorbed, may be formed. They may beformed with a same scanning setting, as part of a same scan, orseparately. In other embodiments, only a percolation zone is formed.Typically, these zones are covered by a tissue flap when the procedureis completed.

At 206, a percolation zone 220 is ablated in area 30 overlying Schlemmcanal 34 and trabecular meshwork 32. If the aqueous humor does notpercolate (208) the ablation step is repeated. In one embodiment of theinvention, once a percolation is detected or a minimal percolation rateis detected (both of which may be manually or automatically detected),the ablation is stopped. In another embodiment of the invention,ablation is stopped or slowed down at points where percolation isdetected, but continued at other parts of area 30 and/or area 31. Aminimal percolation zone may be defined, which is smaller than theactual ablated area of area 30. Thus, the ablation is closed circuit,i.e., iterative, or open circuit ablation can be practiced as well, atleast for the reservoir, for example based on predefined laser beamsettings.

Typically, the tissue in area 30 has a varying thickness, by ablatingmore at areas where there is less percolation, a uniformly thin filterarea may be defined. Alternatively, a uniform (or other profile)percolation distribution can be achieved. Also, percolation-adaptedablation allows a matching of the scanning parameters to the tissuelaser sensitivity. One or more of the following scanning parameters maybe varied over the ablation area, to control the ablation:

-   -   (a) Spot size. A larger spot size provides a lower resolution        and less energy per unit area. In some embodiments, non-circular        spots are used, for example, elliptical, triangular, hexagonal        and rectangular. Alternatively or additionally, a spot pattern        may be provided. Such a pattern may be continuous, for example        Gaussian or uniform, or discrete, for example, checkerboard.        Exemplary circular spot sizes are between 0.1 mm and 1 mm, for        example 0.8 mm.    -   (b) Dwell time. By varying the scanning speed, more energy can        be deposited at locations that are not yet percolating and less        energy at locations where no further ablation is desired. An        exemplary dwell time is between 100 μs and 1000 ms, for example        400 μs.    -   (c) Beam intensity. This may be controlled, for example, by        modulating the laser source or using attenuator 110, or another        attenuator (uniform or spatially modulating) elsewhere along the        optical path. The attenuators may selectively attenuate only the        ablating beam (and not the optional aiming beam) for example        having frequency selective properties or being having a suitable        physical location. In some cases, the beam may be turned off for        part of the scan. An exemplary source beam intensity is between        5 W and 15 W. The actual intensity that should be delivered to        the eye can depend on various parameters, for example, the dwell        time (and spot size), the age of the eye tissue, and the type of        effect desired, e.g., ablation or coagulation. In particular,        increasing the beam intensity can increase the thickness of        ablation.    -   (d) Beam location and scan pattern. In some embodiments, the        beam scans the entire area, regardless of the effects of the        beam. Alternatively, the beam may skip certain location and/or        change the scan area definitions, on the fly, to match the        percolating zones and/or required ablations.    -   (e) Scan path. In some embodiments, the scan path is selected so        that there will be sufficient time to detect percolation at a        location, between repeated ablations of the location.        Alternatively or additionally, the scan path may be changed        responsive to the initiation of percolation at some locations in        the area. Optionally, the scan path overlaps itself, for example        10%. An exemplary scan path is by rows. Optionally, the scanning        is interleaved, with a greater separation between rows. The row        direction may reverse itself every row.    -   (f) Scan shape. Various scan shapes may be used, to achieve        variously shaped percolation and/or reservoir shapes.    -   (g) Laser pulse parameters, such as pulse length, pulse envelope        and pulse repetition rate. In some embodiments, a pulsed laser        is used. The laser may generate a pulsed beam or a continuous        pulsed beam may be further temporally modulated. In one        exemplary embodiment, a CW laser is used and modulated to have        pulses between 1 μs and 1 ms and a repetition between 1 Hz and 1        kHz. Alternatively, a continuous beam is provided at the eye. In        a particular example, pulse duration is reduced, in order to        reduce thermal damage.    -   (h) Local Pulse Rate. This is a composite of several parameters        and defines the rate at which laser pulses will contact a        certain area, thus also defining the time for percolation        between pulses. By matching the local pulse rate to a desired        percolation rate, the thickness of membrane 48 can be set or at        least more closely approximated.

Alternatively or additionally to detection percolation using imageprocessor 68, other feedback mechanisms may be used to control ablation,set ablation parameters and/or to provide alarm signals. Image processor68 is optionally used to detect the thickness of the sclera and/or thedepth of ablation. Several depth and distance measuring methods areknown in the art, for example, using stereoscopic imaging, or bydetecting shadows or changes in patterns of light that are projectedfrom a side light (not shown). Alternatively or additionally, anoptional dedicated sensor 37 (FIG. 1) is used, for example, fordetecting percolation or measuring the thickness of the sclera or thedepth of ablation, for example, optically or using ultrasonicreflection. A thickness sensor may also be used prior to the procedure,for example for mapping (e.g., to set ablation parameters in general orfor different locations).

Alternatively or additionally, an optional contact sensor 35 (FIG. 1) isused to measure the sclera thickness, for example timing ultrasonicreflection from the aqueous humor of the eye. Alternatively oradditionally, sensor 35 detects percolation (e.g., by detecting flow ormoisture) and is located at an area which is not ablated. Optionally,the contact sensor is manually positioned so that the laser radiationdoes not hit it.

Alternatively or additionally to directly monitoring the ablation or thepercolation, an optional sensor 39 (FIG. 1) may be used for monitoringthe pressure in eye 40. Various types of such pressure sensors may beused, for example sensors which require applying pressure to the eye.Possibly, such sensors did not find use during surgery in previoustimes, due to fears of a possible interaction between such pressure(which may be deforming) and the delicacy of the procedure or theforcing of fluid from the eye. A potential advantage in accordance withan exemplary embodiment of the invention is the ability to receivefeedback in real-time or near real-time on the effect of a part of theprocedure, so that a more finely tuned effect on intra-ocular may beachieved.

When percolation is achieved, it is expected that the intra-ocularpressure will go down. However, after a time, the pressure may go up,stay steady, go down or oscillate for a while. The time until a steadypressure is achieved may be as long as several weeks or as short as afew minutes. However, it is expected that for some situations (e.g.,initial pressure, type of ablation pattern, speed of response, degree ofresponse) the behavior of the pressure can be estimated. Optionally,different changes in pressure profiles are stored and are used toidentify the degree of percolation under different conditions (e.g., byaccumulating a database of profiles and results). In an exemplaryembodiment of the invention, two types of pressure reductions aredistinguished, an immediate pressure reduction and a long term pressurereduction. Thus, for example, when percolation first occurs, thepressure is expected to go down to a lower level. This distinction, may,in some cases, be a simple modeling of an exponential decrease inpressure. In some cases, for example, the procedure is stopped when areduced pressure 16 mm is achieved, even though a final expected anddesired pressure is 12 mm. In other cases, the procedure may be stoppedat 12 mm, and the pressure will then climb up to 16 mm, for a steadystate final pressure. Optionally, detection of intra-ocular pressurereduction is used to automatically modify ablation parameters and/or tostop ablation. For example, the ablation pattern area may be reduced ifpressure reduction is found. Alternatively, if a pressure reduction isnot sufficient, the ablation pattern may be enlarged and/or pulse orscanning parameters (e.g., as described herein) changed. In a simplecase, changes in pressure are used to decide if to stop the procedure.

The input from the sensor (or imaging system) may be used manually orautomatically, depending on the implementation. For example, controller74 may analyze and respond to input form such sensors automatically.Alternatively or additionally, a user reads the sensor readings andinputs new parameters into controller 74, for example using input 76.Alternatively or additionally, a user enters the sensor reading into theinput and controller 74 analyses the input to determine a response. Onepotential advantage of such user intermediate activity is that there isno need to electrically couple the sensor to the ablation system and anyexisting sensor may be used.

Alternatively or additionally to storing pressure profiles, ablationrate profiles may be stored, with the understanding that as percolationinitiates and processes, the ablation rate will go down. Such ablationprofiles (e.g., thickness profiles) may be used to assess theprogression of the procedure and/or to indicate alarm conditions.

At 210, reservoir 222 (FIG. 6) is optionally created. Instead of usingpercolation to detect the reservoir depth, it may be estimated based onthe laser energy deposition or it may be determined using imageprocessor 68. In some embodiments, reservoir 222 is created while orprior to creating percolation zone 220.

FIGS. 6A and 6B illustrate a completed percolation (220) and reservoir(222) system, from a side and a top view, in accordance with anexemplary embodiment of the invention.

FIG. 6A shows the situation after flaps 26 and 27 are closed. FIG. 6B isa top view, with the flaps shown as a dotted line.

As shown, reservoir 222 and percolation zone 220 have differentgeometries, which can include different shapes, sizes and/or depths. Inan exemplary embodiment, percolation zone 220 is 3×3 mm and reservoir222 is 5×3 mm. Alternative exemplary sizes for percolation zone 220 arebetween 2 and 5 mm by between 2 and 5 mm. Alternative exemplary sizesfor reservoir 222 are between 3 and 5 mm by between 3 and 5 mm. Theactual sizes of the zones may be fixed. Alternatively, one or both sizesdecided ahead of time based on patient characteristics, for example,eye-size, age and intra-ocular pressure. Alternatively or additionally,the actual sizes may be decided during the procedure, for example, basedon the percolation rate. Alternatively or additionally, the sizes ofpercolation zone 220 and/or reservoir 222 may be adjusted (up or down)in a later procedure.

However non-rectangular shapes can be provided, for example, round,elliptical or polygonal with, for example, between 3 and 10 facets. Inparticular, both convex and concave forms may be provided, for exampleto provide different perimeter-area ratios for reservoir 222 and/orpercolation zone 220. Alternatively or additionally, at least part ofone of the zones may be provided as a plurality of elongated zones.

Alternatively to contiguous reservoir and percolation zone, the two maybe separated by one or more channels, for example a channel ablated inthe sclera.

In some cases, ablation may cause charring of the eye or deposition ofdebris. Optionally, such charring is cleaned away using fluid or a wipe.

Optionally, prior to closing the flaps, a spacer is insert to maintainreservoir 222 and/or percolation zone 220 open (212), at least until thespacer is absorbed, as some spacers are formed of a bio-absorbablematerial. Exemplary spacers are:

-   -   (a) AquaFlow by Staar inc., formed of collagen;    -   (b) SK-Gel by Corneal Co., formed or reticulated hyaluronic        acid;    -   (c) Hydrogel implants of various designs; and/or    -   (d) Scleral implants formed of left over or harvested pieces of        ocular tissue.

Alternatively or additionally to a spacer, an anti-metabolic materialmay be provided at the ablated area, to retard tissue ingrowth.Exemplary materials include: Mitomycin, typically contact-applied as adamp sponge for 2-3 minutes and 5-Fluoro-Uracil (5FU), typically appliedas a series of sub-conjectival injection after the procedure.

At 214, the flaps are closed and sealed, for example using a laser,adhesive or by sewing.

Alternatively to scanning, in one embodiment of the invention, a largespot size is used, to cover the entire ablation area. Optionally,ablation will stop at portions of the ablated area that percolate, forexample by a mechanism of the laser light being absorbed by thepercolating aqueous humor only at the sufficiently ablated locations.

In another alternative to scanning, the procedure may be performedfree-hand. Optionally, an integral scanner is provided in the probe. Anaiming beam, which may be scanned or not, may be used to show the scanboundaries.

In an exemplary embodiment of the invention, the self-limiting behaviorof the laser interaction with the sclera is used as a control feature ora safety feature, depending on the laser and on the degree of certainty.In one example, the self-limiting behavior is used as a control feature.The laser is set to have an ablation depth (e.g., power, pulse length)equal to the expected percolation rate when a desired membrane isachieved. This percolation rate may depend, for example, on theintra-ocular pressure and/or on other parameters, such as results from aprevious or a same operation on the patient. Another possible setting isa matching between ablation depth in sclera and in fluid. This settingmay vary, for example, if the sclera or intra-ocular fluid are dyed orotherwise have significantly different absorption at the laserwavelength. Optionally, the scan settings are modified to provide alocal pulse rate that matches the expected percolation rate. In anexemplary embodiment of the invention, the power setting is 3 J/cm² andthe pulse duration is 1 ms. Higher power, such as 10 or 20 J/cm² at thispulse duration will provide a greater ablation depth. Exemplarydurations are thus between 1-2000 μs, for an isotopic CO₂ laser.Exemplary power levels are between 2.5 and 50 J/cm². In contrast, anErbium:YAG can work at 1.5 J, but has undesirable self-limitingbehavior. The exact power setting may depend of course on the exactspectral wavelength of the laser and/or on the absorbencycharacteristics of the sclera. Also, the sclera and/or the percolatingfluid (e.g., the eye) may be dyed to have desired absorbencycharacteristics.

The procedure as described above is applied. Once the percolation isfast enough, the ablation effectively stops and the operator can stopthe laser. Alternatively, the automatic vision system is used to stopthe procedure once it is determined that no further ablation of sclerais being achieved.

In a safety method, the same setting settings are applied, However, theoperator does not trust the system or is worried that thermal damage maybe caused by repeated ablation of fluid. Instead, the operator sets theablation depth and ablates until he sees fluid and then ablates at aslower rate (e.g., using less often applied manual “zap” instructions)and/or at a lower ablation thickness setting, until the percolation rateappears to be correct. If the operator makes a mistake, the ablationshould not penetrate through the sclera, as it is self-limiting.

It should be noted that the same procedure, possibly with differentparameters may be applied to a wide range of patients. These patientsmay be characterized, for example, by different percolation rates and/ordifferent target percolation rates. For example, the non-penetratingfiltration procedure may be applied as a precautionary measure or inpatients with slightly elevated intra-ocular pressures, such aspressures, between 14 mmHg and 21 mmHg or below 30 mmHg.

FIG. 7 illustrates an exemplary protective framework 300, in accordancewith an embodiment of the invention. Framework 300 is optionallyattached to microscope 58 and blocks laser light from reaching outsideof the ablation areas 30 and 31 and/or a safety zone defined aroundthem. Alternatively or additionally, framework 300 may be attached tothe patient. As shown, framework 300 comprises an attachment extension302 for attaching the framework and a frame 304 defined, in thisembodiment, by four bars. These bars may be wider than shown and/or mayhave a curtain attached to them for example a disposable adhesive (tothe framework) curtain. The required focal distances of the procedureare optionally set using framework 300. A distance adjustment screw 306may optionally be provided. Alternatively or additionally, frameworkgeometry defining screws 308 may be provided, to control the shapeand/or size of the framework and, thus, the ablateable zone. In someembodiments, frame 300 is not rectangular, for example being formed of apliable wire. Alternatively or additionally, frame 300 may besemi-transparent, but not to except to beam 54. In one example, frame700 comprises a holder, for example a clip, for a transparent plate thedefines the laser action area.

FIGS. 8A and 8B illustrate two alternative exemplary eye protectors inaccordance with some embodiments of the invention.

FIG. 8A shows an aperture type protector 400, comprising a body 402 thatblocks laser light and an aperture 404 which passes laser light. In oneembodiment of the invention, body 402 is flexible and adhesive, forexample being a silicon rubber sheet. Optionally, body 402, whenattached to eye 40, maintains flaps 26 and 27 open. Alternatively tobeing flexible, body 402 may be rigid or plastically deformable.Alternatively to adhesive, other attachment methods, such as suturing,vacuum and/or self adhesion to the eye surface based on mechanicalproperties of the eye surface and/or body 402, may be used instead.Protector 400 may be disposable or sterilizable. Optionally, aperture404 (or window 410, below) defines the shape of the ablation areasand/or shape of the flaps, for example if the flaps are cut using alaser.

FIG. 8B shows a window type protector 410 having a body 412 which can bethe same as body 402. However, instead of an aperture 404, a window 414may be provided for selective transmission of laser light. As shown,window 414 may protrude, for example towards the microscope, optionallyto provide contact with the optical path and/or towards the eye, forexample fitting into areas 30 and 31. Alternatively, a flat window maybe provided. In an exemplary embodiment of the invention, window 414 isformed of a laser sensitive material, that turn opaque after a certainamount of energy is deposited in it, preventing inadvertent damage tothe eye.

Alternatively, protector 410 may be attached to the microscope, forexample using adhesive or being formed as a slide that can be coupled tothe microscope. Alternatively to a slide, movable shutters are providedto limit the possible positions of the laser beam on the eye.

It will be appreciated that the above described methods of selectiveablation of sclera and corneal tissue may be varied in many ways,including, changing the order of steps and the types of tools used. Inaddition, a multiplicity of various features, both of method and ofdevices have been described. In some embodiments mainly methods aredescribed, however, also apparatus adapted for performing the methodsare considered to be within the scope of the invention. It should beappreciated that different features may be combined in different ways.In particular, not all the features shown above in a particularembodiment are necessary in every similar embodiment of the invention.Further, combinations of the above features are also considered to bewithin the scope of some embodiments of the invention. Also within thescope of the invention are surgical kits which include sets of medicaldevices suitable for performing a single or a small number filtrationprocedures. When used in the following claims, the terms “comprises”,“includes”, “have” and their conjugates mean “including but not limitedto”.

It will be appreciated by a person skilled in the art that the presentinvention is not limited by what has thus far been described. Rather,the scope of the present invention is limited only by the followingclaims.

1. Apparatus for ophthalmic surgery on an eye comprising: a laser sourcethat generates a laser beam, adapted to ablate a sclera tissue thicknessof between 5 and 30 microns in a single shot, without causingsubstantial shockwave or thermal damage to said eye, said beamcontacting said eye for at least one of a dwell time of above 100micro-seconds and a spot size of over 100 microns; and an ophthalmiclyeffective position controller adapted to aim said beam at said eye fromoutside said eye.
 2. Apparatus according to claim 1, comprising anophthalmic microscope operative to view an eye during an ophthalmicprocedure that uses said laser beam.
 3. Apparatus according to claim 2,comprising a monitor for displaying a view of said tissue removal viewedby said microscope.
 4. Apparatus according to claim 2, comprising a beamcombiner for combining a line of sight of said laser and saidmicroscope.
 5. Apparatus according to claim 1, wherein said positioncontroller comprises an ophthalmic frame operative to fixing a relativeposition and angle of said laser source and an eye of a patient. 6.Apparatus according to claim 1, wherein said position controllercomprises a scanner comprising an input for said laser beam and anoutput of a spatially scanned laser beam.
 7. Apparatus according toclaim 6, comprising controlling circuitry that drives said scanner toremove tissue in a desired pattern on the eye.
 8. Apparatus according toclaim 7, comprising a sensor which monitors an indication of progressionof said surgery, on said eye, to produce a progression signal. 9.Apparatus according to claim 8, wherein said sensor comprises: a camerawhich acquires an image of said tissue removal; and an image processorthat processes said image.
 10. Apparatus according to claim 8,comprising circuitry that uses said progression signal to generate anindication of the tissue removal state.
 11. Apparatus according to claim10, wherein said circuitry uses said indication to close a control loopof said tissue removal.
 12. Apparatus according to claim 10, whereinsaid indication of tissue removal state comprises an indication of thethickness of remaining tissue in the area of tissue removal. 13.Apparatus according to claim 10, wherein said indication of tissueremoval state comprises an indication of a percolation rate through theremaining tissue in the area of tissue removal.
 14. Apparatus accordingto claim 8, wherein said sensor measures an intra-ocular pressure. 15.Apparatus according to claim 8, wherein said sensor is a non-penetratingsensor.
 16. Apparatus according to claim 8, wherein said sensor is acontact sensor.
 17. Apparatus according to claim 8, wherein saidcontrolling circuitry receives signals from said sensor.
 18. Apparatusaccording to claim 8, comprising a user input, wherein said controllingcircuitry is adapted to receive and interpret entries on said input asindicating signals from said sensor.
 19. Apparatus according to claim 1,comprising a frame attached to said combiner, which frame blocks saidlaser beam from at least one part of said eye.
 20. Apparatus accordingto claim 1, wherein said laser source comprises a CO₂ laser source. 21.Apparatus according to claim 1, wherein said laser source comprises anisotopic ¹³C¹⁶O₂ laser source.
 22. Apparatus according to claim 1,wherein said laser source comprises an Erbium:YSGG laser source. 23.Apparatus according to claim 1, wherein said laser source comprises adiode laser source operated at a wavelength near 1.8 microns. 24.Apparatus according to claim 1, wherein said laser source comprises a UVlaser source.
 25. Apparatus according to claim 1, wherein said lasersource generates a second, visible wavelength, aiming beam aligned withsaid laser beam.
 26. Apparatus according to claim 1, wherein said laserbeam is a pulsed laser, each pulse being a single shot.
 27. Apparatusaccording to claim 1, wherein said laser beam is a pulsed laser, aplurality of pulses being grouped as a single shot.
 28. Apparatusaccording to claim 1, wherein said laser beam is a continuous laser thatis artificially gated to generate shots.
 29. A method of performing anon-penetrating filtration procedure, comprising: opening a flap in aneye, overlying a Schlemm's canal of said eye; forming a percolation zoneadjacent said Schlemm's canal by ablation using a laser that ablates atissue thickness of between 5 and 30 microns, each shot; forming areservoir in a sclera of said eye and in fluid connection with saidpercolation zone; and closing said flap.
 30. A method according to claim29, wherein forming a percolation zone comprises cleaning away charredtissue from said percolation zone.
 31. A method according to claim 29,comprising forming by automatic scanning with a laser.
 32. A methodaccording to claim 31, wherein automatic scanning with a laser comprisesautomatically controlling at least one parameter of the scanningresponsive to an effect of the laser on the tissue.
 33. A methodaccording to claim 29, wherein said laser is a CO₂ laser.
 34. A methodaccording to claim 33, wherein said laser is a ¹³C¹⁶O₂ laser.
 35. Amethod according to claim 33, wherein said laser is an Er:YSGG laser.36. A method according to claim 33, wherein said laser is a diode laseroperated near 1.8 microns wavelength.
 37. A method according to claim29, comprising placing a protective sticker on said eye prior to formingsaid percolation zone, said protective sticker having a spatial windowthat admits a wavelength of said laser and a body that block saidwavelength from parts of the eye other than an area to be ablated.
 38. Amethod of performing a non-penetrating filtration procedure, comprising:forming a percolation zone adjacent a Schlemm's canal of an eyemeasuring an intra-ocular pressure of said eye in response to saidforming a percolation zone; and modifying parameters of said forming inresponse to said measuring.
 39. Apparatus according to claim 1, whereinsaid dwell time is over 100 micro seconds.
 40. Apparatus according toclaim 1, wherein said spot size is over 100 microns.
 41. Apparatusaccording to claim 26, wherein each shot has a duration of over 1milliseconds.
 42. Apparatus according to claim 6, wherein said circuitryis configured to remove sclera tissue in the shape of a reservoirsuitable for non-penetrating trabeculectomy.
 43. Apparatus according toclaim 6, wherein said circuitry is configured to remove sclera tissue inthe shape of a percolation area suitable for non-penetratingtrabeculectomy.
 44. Apparatus according to claim 1, wherein said beamhas a power of over 5 watts.
 45. Apparatus according to claim 1, whereinsaid laser ablates between 10 and 30 microns in a single shot. 46.Apparatus according to claim 1, wherein said laser ablates between 16and 25 microns in a single shot.
 47. Apparatus according to claim 1,wherein said laser ablates between 16 and 20 microns in a single shot.